In the manufacture of waterproof garments and other waterproof fabric assemblies having stitched seams at intersecting areas of cloth, it is often advantageous to seal such seams with a seam tape. This is especially necessary wherein the seams would violate the integrity of the waterproofing, if not for the application of such a seal. The present invention is particularly useful for seam sealing of waterproof garments made from Gore-Tex fabric laminates, but would be generally useful for any sealing operation used to preserve the integrity of the waterproof properties of joined fabrics or generic fabric laminates.
Seams are typically sealed using a seam tape made of a fabric similar to the fabrics comprising the seam to be joined, and having a hot-melt polyurethane adhesive on one side of the tape. A nozzle emits a stream of hot air directed at the tape sufficient to activate the hot-melt adhesive, and the tape and the seam are cooperatively pressed together between a pair of nip rollers to bind the adhesive tape over the seam.
Specifically, waterproof garments made from Gore-Tex fabric laminates are manufactured using Gore-Seam sealing machines to perform the sealing operation, but other manufacturers make and use machines performing similar duties. To assure seams of consistent quality are manufactured using such machines, it is important to position the nozzle precisely in the optimum location to apply the stream of hot air uniformly to the tape to evenly melt the adhesive, thus enabling creation of a perfect seal each and every time. Typically, the requirement for precision in location has been met through the use of positioners adjustable in each of the three degrees of freedom (vertical, first horizontal, second horizontal substantially perpendicular to first horizontal) to position an arm onto which the nozzle is mounted. To enable quick loading and unloading of the garments to be sealed in such machines, the arm is capable of being moved in and out of the precise position quickly, usually through the use of an automatic actuator.
Typically, the nozzle is part of a nozzle assembly which consists of a nozzle body connected to an air manifold having a configuration necessary to transport the hot air from a hot air supply to the desired location of the nozzle body. Typically, the manifold comprises metal tubing welded to the nozzle body at one end and welded to a screwed coupling at the other end for connection of the nozzle assembly to the hot air supply.
As metal tubing is inherently difficult to bend or weld to tight tolerences, each nozzle assembly therefore has slightly different dimensions. Similarly, a typical screwed coupling does not allow repeatable realignment of the nozzle assembly if it must be removed for any reason, such as for cleaning. Therefore if the nozzle assembly on a machine must be removed or replaced, the positioners must be re-adjusted in each degree of freedom to precisely reposition the nozzle in relation to the work area. Repositioning may be a time-consuming operation that increases the overall manufacturing time, and/or it may cause some off-quality product rejects due to trial and error, thus wasting product.
The seams made with a seam-sealing machine are typically still the weakest link in the overall waterproof property of the garment, because the adhesive seal holding the tape over the seam eventually may fail.
During the manufacture of the seams, the seam sealing machine operators prefer to observe the interface of the sealing surfaces during the operation to assure correct alignment of the seam tape with the seam. Prior nozzle designs have tended to place the nozzle directly in front of the seam interface, thus obscuring the vision of the machine operator. Again, any number of nozzle uses might be similarly disadvantaged by a nozzle design that obstructs the nozzle operator's view of the article at which the nozzle is directed.
The heat of the hot air exiting the nozzle is also critical to proper adhesive melting and subsequent attachment. Prior nozzle designs have been equipped with a thermocouple on the hot air supply, thereby measuring the air temperature prior to the radiative heat loss from the tubing between the thermocouple and the nozzle outlet. Use of a thermocouple so placed does not measure the true air temperature at the exit of the nozzle, which is the critical temperature for the adhesive melting operation, and foreseeably would be a critical temperature for other hot air nozzle uses.
The prior art generally discloses nozzles of any number of configurations for heat welding or hot air seam sealing, none of which specifically address the problems discussed herein. It is the object of the present invention, therefore, to provide a nozzle assembly adapted for repeatably positioning the nozzle in a precise relationship to the article to receive the air stream. It is a further object of the invention that the nozzle assembly enable the nozzle to be removed and replaced in the same position relative to the article. It is a feature of the present invention to provide such a nozzle assembly that can be used without obscuring the nozzle operators vision of the article, such as a seam sealing tape. A still further feature of the present invention is to incorporate a thermocouple integral to the nozzle to provide temperature measurement close to the nozzle exit.